Ron Vlaar has revealed he could yet sign a new deal with Aston Villa this summer.
Goalkeeper Jason Brown has left Aberdeen with immediate effect.
The Wales international made 28 appearances for the Dons after arriving from Blackburn 18 months ago, but has been unable to displace Jamie Langfield his season.
Pittodrie chief executive Duncan Fraser told the club's official website: "Jason made it clear to us he was keen to return to England and continue his career.
"He is a proud member of the Welsh international team and in order to maintain his place in the squad he feels it is vital for him to be playing every week.
"The club wish Jason all the best with his future career."